Mechanical rotary acceleration sensor



May 18, 1965 E. J. MCQUILLEN MECHANICAL ROTARY ACCELERATION SENSOR FiledMay 51, 1963 mw mmon m .Sm

Nh ON INVENTOR.

EDWARD J. MCQUILLEN A i TORNEY United States Patent O 3,183,724MECHANICAL ROTARY ACCELERATION SENSOR Edward J. M'cQuillen, HuntingdonValley, Pa., assigner to the United States of America as represented bythe Secretary of the Navy Filed May 31, 1963, Ser. No. 284,755

1 Claim. (Cl. 73-514) (Granted under Title 35, U.S. Code (1952), sec.266) bination reel and launcher assembly is secured to the towingaircraft. The reel ris capable of towing a 200 lb. target at the end of80 to 100,000 feet of tow line at speeds up tok Mach 2. In addition, itis capable of reelingthe :target in and out at a speed of 60 miles perhour. To accomplish this, a ram air power unit with reversible pitchblades is utilized to drive the reel or tow line storage spool, thepitch of the propeller blades determining reel in or reel out. In orderto preclude the power unit, tow line, and target secured thereto fromaccelerating beyond acceptable limits during the reeling operation, anelectronic acceleration monitor is provided which energizes anelectrical relay when a predetermined value of rotary acceleration isexceeded. This in turn opens a Contact and deenergizes the blade pitchchange motor to stop the blade rotation, thereby causing a decelerationof the power unit within acceptable ranges of acceleration, Uponreaching these acceptable limits the blade pitch change motor will againbegin to rotate the propeller blades. The cost of the present electronicsensor is extremely high and in view of its complex nature, sincetransistors, capacitors, resistors, relays, etc. are utilized, thereliability has failed to meet the high operating standards required.Furthermore, the electronic monitors have been found sensitive to thetemperatures encountered in tow target applications, these temperaturesreaching 54 C. and introducing senious error in the monitoringoperation.

It is an object of the present invention to provide a simply operatedand inexpensive mechanical acceleration sensor for monitoring the rotaryacceleration of a rotating element.

Another object of 'this invention is to provide a mechanical rotaryacceleration device for sensing both acceleration and deceleration of arotating member.

An additional objectof this invention is to provide a rotaryacceleration sensor of high sensitivity, reliability and accuracy andone which is satisfactorily operable at extreme ranges of temperatureconditions.

Various other objects and advantages will appear from the followingdescription of an embodiment of the invention and the novel featureswill be particularly pointed out hereinafter in connection with theappended claim.

In the drawing:

FIG. 1 is a sectional view of the rotary acceleration sensor; and

FIG. 2 is a side view of the sensor of FIG. l with the cover removed forpurposes of clarity.

ln the illustrated embodiment of the invention and rst referring to FIG.1, the rotary accelerations sensor is generally indicated at includes aframe or support member 11 housing a gear box 12 which has a stub shaft13 extending therefrom and through the support rnem- 3,183,724 PatentedMay 18, 1965 Mice ber 11. This outwardly extending shaft 13 is formedfor connection by coupling 14 to a rotating shaft 16, the accelerationof which is to be monitored by the sensor 1t). Both coupling 14 andshaft 16 are illustrated by dotted lines.

The output of gear box 12 is connected through shaft 18 to pinion gear19 which in turn supplies rotational driving forcefor the bevel geardifferential mechanism generally noted at 20. Differential mechanism 20comprises a side assembly 21 including an input spur gear 22 meshingwith the teeth on pinion gear 19 and an end gear 23. A similar sideassembly 26 includes spur gear 27 and end gear 28, the spur gear 27having an inential rotor member 29 secured thereto by means of screws orother appropriate means. Inertial member 29 is discshaped, coaxiallydisposed with the side assembly 26 and is further of computed mass.

A spider generally indicated at 30 is interposed between the two sideassemblies 21 and 26 and includes a pair of spider gears 32 and 33rotatably mounted at the ends of a cross-shaft 34. Cross-shaft 34 ispinned or otherwise xedly secured intermediate the ends thereof to aspider shaft 35 having the ends thereof rotatably mounted within thesupport member 11. Whereas the spider 30 is rigidly fastened to thespider shaft 3S, side assemblies 21 and 26 and the inertial rotor membersecured to side assembly 26 are coaxially disposed about and rotatablymounted on the spider shaft 35 by roller bearing assemblies 4d.

An end 36 of spider shaft 35 extends through the frame member 11 and hasa relatively thin disc element 45 of predetermined area rigidly securedat fits center to the terminal portion of shaft 35. A chamber orenclosure 46, shown exaggerated for purposes of clarity, is rigidlysecured to the frame member 11 by appropriate means and contains aviscous damping fluid 47 such as silicon oil or the like of preselectedand predetermined viscosity. Appropriate sealing members 48 and 49 areprovided to preclude the duid 47 from escaping from the enclosure 46.The clearance between the disc member 45 and its enclosure is sized todevelop the desired viscose shear stress in the tiuid in order tocritically dampen any osoillation of the spider shaft 35. The shearclearance, the shearing area, and the liuid viscosity of the silicon oilare all evaluated and determined for the purpose of obtaining criticaldamping, that is, to obtain an accurate indication of the accelerationin the shortest length of time. Critical damping is desired inopposition to overdamping or underdampiing since underdamping willprovide overshoot or shaft oscillation of too great a value and anextended period of time will elapse before a true and accurate value ofacceleration could be determined. In the case of overdamping, althoughan accurate acceleration value will be reached Without undue oscillationof the shaft 35, this will be obtained in -a slow, continuing mannerwhich will result in the elapse of a prolonged period of time.

In order to eliminate any dead zone in the rotation of the spider shaft35 and the inaccuracies that result therefrom, a pair of preloadedtorsion springs 50 and 51 are interconnected between the frame member 11and the shaft 35 and each is stressed in opposition to the other.

The springs 50 and 51 are of selected strength and are identicallypreloaded in order to preclude the rotation of shaft 35 except underpreset and predetermined conditions of acceleration of the input shaft16.

For the purposes of sensing acceleration above a preset value andcontrolling same, an yarm element 55 of nonconductive material istixedly keyed to shaft 35 at the end thereof and is housed within switchenclosure generally noted at 6l). Enclosure 60 includes a non-conductivespacer element 61 of plastic or other appropriate material enea, afi

having notches 62 formed therein for retaining and spacing a pluralityof parallel, highly resilient switch contact members 65 which includebutton contacts o6. A pair of switch members 65 are placed on each sideof the arm S5, with one pair noted at A interconnected with anacceleration controller 7d by electrical conductors 7l; and the otherpair noted at D interconnected with a deceleration controller 72 byconductors 73. '72 may mechanically or electrically regulate therotation of shaft lo.

Although the disclosed embodiment illustrates the output of shaft 35being utilized to operate a switch for actuating a rotational controlunit, this invention is applicable for other purposes, such as providinga signal to an operator on a control panel when acceleration exceeds thepredetermined value or moving a wiper arm on a potentiometer to provideconstant monitoring of the change in Velocity of a rotating body.

In operation, the accelerator sensor l@ is joined by coupling ld to aninput shaft i6 for purposes of measuring or indicating the accelerationof the rotating input shaft 16 and the appropriate measuring, indicatingor control unit is electrically connected to switch A and switch D attheir lower terminal portions. When the input shaft rotates at aconstant velocity, that is where there is no acceleration ordeceleration, the side assembly 2 will rotate at a proportional Velocitydetermined by the gear ratios within gear box l2 and the relationshipwith pinion gear i9 and input spur gear 22. This constant velocityrotation will be transferred by spider 3) to side assembly 26 andcontiguous inertial rotor member 29, it being noted that the sideassembly 26 and rotor Z9 will rotate in a direction opposite to therotation given the side assembly Zl.. In this condition of constantvelocity the spider gears 32 and 33 rotate about the carrier shaft 3ftbut no rotation of 34 will occur. When there is a change in the velocityof the input shaft f6, that is, where there is an acceleration ordeceleration, this motion will be transmitted to the side assembly 2l.However, Clue to the effects of the inertial rotor member 29, theassembly 26-29 will tend to rotate at the prior initial and constantvelocity thereby creating a differential speed which will be rereflectedby rotation of the cross-shaft 3d thereby rotating the spider shaft 35in response thereto. The direction of rotation of spider shaft 35 willdepend upon whether the input shaft 16 has been accelerated ordecelerated. When its rotational movement is of suficient extent toovercome the resistance of torsional springs 50 or 5l, arm 55, held in acentral position intermediate the adjacent pair of switch A and D by theplacement of the preloaded torsion springs, will rotate and urge contacted of adjacent resilient switch element 65 to make contact with theother element 6d.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claim the invention maybe practiced otherwise than as specically described.

What is claimed is:

A device for accurately sensing and controlling speeds of rotation ofrevolving bodies comprising:

a support member,

The controllers 7h and an output shaft journaled for rotation withinsaid support member,

first input gear means rotatably supported on said shaft and including aspur gear and a first end gear assembly,

transmission means including a gear box secured to said support memberhaving a stub shaft extending therefrom and formed for connection to therevolving body and further including a pinion gear extending from saidgear box engaging said spur gear of said first input gear means,

second input gear means rotatably supported on said shaft and includinga second end gear assembly and a spur gear having a disc-shaped inertialrotor member rigidly secured thereto and coaxially disposed about saidoutput shaft, said inertial rotor member being of predetermined mass andalso freely rotatable about said shaft,

differential gear means including a pair of spider gears engaging saidadjacent first and second end gear assemblies and being rotatablysecured at each end of a rod member, said rod member being xedintermediate its ends to said output shaft to rotate said shaft whensaid first and second input gear means rotate at different speeds,

a pair of equally preloaded torsion springs each secured between saidsupport member and said output shaft in opposition to the other toprovide a predetermined rotational resistive force,

critical damping means including a relatively thin disc member rigidlysecured to said output shaft and rotatable within a housing containingdamping uid for precluding oscillation of said output shaft,

an arm member rigidly secured to said output shaft and rotatabletherewith,

a pair of parallel ilexible switch members adjacent each side of saidarm and including Contact members intermediate the length thereof,

and conducting means electrically interconnected between each of saidpairs of switch members and a speed control circuit whereby said controlcircuit is energized when one of said Contact members is urged by saidarm into contacting relationship with the other of said contact memberswhen the acceleration of the revolving body exceeds at predeterminedvalue.

References Cited by the Examiner UNITED STATES PATENTS 2,159,778 5/39Bush l88-l8l 2,198,032 4/40 Farmer 73-5l4 2,403,605 7/46 Lesnick 73-5072,435,319 2/48 McCune 73-514 2,595,195 4/52 Hosterman 73-507 2,900,4658/59 Weiss 20G-61.46

FOREGN PATENTS 4l7,389 10/34 Great Britain.

REC RD C. QUESSER, Primary Examiner.

JAMES l. GiLL, Examiner.

